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11100B–ATARM–31-Jul-12
SAM4S Series [Preliminary]
Preserved
Preserved by writing the same value back that has been previously read from the same field on the
same processor.
Read
Reads are defined as memory operations that have the semantics of a load. Reads include the Thumb
instructions LDM, LDR, LDRSH, LDRH, LDRSB, LDRB, and POP.
Region
A partition of memory space.
Reserved
A field in a control register or instruction format is reserved if the field is to be defined by the
implementation, or produces Unpredictable results if the contents of the field are not zero. These fields
are reserved for use in future extensions of the architecture or are implementation-specific. All
reserved bits not used by the implementation must be written as 0 and read as 0.
Thread-safe
In a multi-tasking environment, thread-safe functions use safeguard mechanisms when accessing
shared resources, to ensure correct operation without the risk of shared access conflicts.
Thumb instruction
One or two halfwords that specify an operation for a processor to perform. Thumb instructions must be
halfword-aligned.
Unaligned
A data item stored at an address that is not divisible by the number of bytes that defines the data size
is said to be unaligned. For example, a word stored at an address that is not divisible by four.
Undefined
Indicates an instruction that generates an Undefined instruction exception.
Unpredictable
One cannot rely on the behavior. Unpredictable behavior must not represent security holes.
Unpredictable behavior must not halt or hang the processor, or any parts of the system.
Warm reset
Also known as a core reset. Initializes the majority of the processor excluding the debug controller and
debug logic. This type of reset is useful if debugging features of a processor.
Word
A 32-bit data item.
Write
Writes are defined as operations that have the semantics of a store. Writes include the Thumb
instructions STM, STR, STRH, STRB, and PUSH.
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